SMPS Inductor values

[Piddling]

Hello all. What brings me to this first post (thanks for letting me join) is I'm repairing a guitar am with a SMPS; I'm needing a bit of help with the inductor.

This snippet from the schematic is for the 6.3v section coming off the transformer, through this circuit then to the main board to power the heaters for the tubes. Aside from the tubes not lighting up there is noticeable burning at the connector for this section, and the PCB under the components in the green box (invertor is in the red box), indicating a voltage jump much higher than the 6.3 volts that should be going through it. Circuits on the main board being fed by other 2 connectors (for other voltages) off this SMPS board indicate they are working.

After going over everything with a meter I'm pretty sure the inductor is gone. My problem is that 2UH drum-type pcb-mount inductors don't appear to be common and/or available. That leaves me with a few questions like:

- can I modify a SM inductor to work?
- is there a way to modify the values of the other components so I can use a more available 2.2 UH or other inductor?

At this point I don't know much about the inductor other than what is on this diagram, nor do I know the current coming out of the transformer into it. I understand inductors and capacitors do similar things, so I'm wondering if it would be possible to balance a new capacitor against a different inductor value.

I can post the entire power supply section if necessary.

Thanks.

 

[ChrisP58]

Can you please post the rest of the power supply schematic? That fragment doesn't look much like a switching supply, but I could be wrong.

Need more info.

 

[ronsimpson]

L106, the value is not critical. 2uH or 2.2uH or 3.3uH. If I only had a 4.7 I would use it. I do not like going down to 1uH but it will work.
I am more concerned that the inductor can handle the current. I don't know what the load is.
Because you have a drum inductor you can see the wire. Verry approximately the wire size and the current carrying ability of the coil are related. If you found a drum coil with the same wire or a little larger that is good.

You can use surface mount inductors.

D108 is a 100 volt 20A Schottky fast diode. That indicates it is a switching power supply.
L108 Bead. That indicates it is a switching power supply.
L106 is only 2uH. It is removing high frequency noise not low frequency noise. That indicates it is a switching power supply.
The three capacitors are very large. Normally switching power supplies do not need large caps.

 

[MrAl]

Hello all. What brings me to this first post (thanks for letting me join) is I'm repairing a guitar am with a SMPS; I'm needing a bit of help with the inductor.

This snippet from the schematic is for the 6.3v section coming off the transformer, through this circuit then to the main board to power the heaters for the tubes. Aside from the tubes not lighting up there is noticeable burning at the connector for this section, and the PCB under the components in the green box (invertor is in the red box), indicating a voltage jump much higher than the 6.3 volts that should be going through it. Circuits on the main board being fed by other 2 connectors (for other voltages) off this SMPS board indicate they are working.

View attachment 147713

After going over everything with a meter I'm pretty sure the inductor is gone. My problem is that 2UH drum-type pcb-mount inductors don't appear to be common and/or available. That leaves me with a few questions like:

- can I modify a SM inductor to work?
- is there a way to modify the values of the other components so I can use a more available 2.2 UH or other inductor?

At this point I don't know much about the inductor other than what is on this diagram, nor do I know the current coming out of the transformer into it. I understand inductors and capacitors do similar things, so I'm wondering if it would be possible to balance a new capacitor against a different inductor value.

I can post the entire power supply section if necessary.

Thanks.

Do you know how much current is drawn from the output 6.3 volts?
You should get an inductor that is rated for the full load current. If it was any less, it could saturate.
You might even be able to make a hand wound air core inductor because 2uH is not much.